The present invention pertains to a mudsaver valve and flowback valve assembly for use in well drilling and casing installation operations.
In the art of well drilling operations, including operations to install well casing, it is common practice to fill the tubular drillstem or casing with drill cuttings evacuation fluid and circulate such drilling fluid or so-called xe2x80x9cmudxe2x80x9d through the drillstem or casing and the wellbore. In this regard, so-called mudsaver valves are usually connected to the lower end of the hollow drillstem drive member or kelly or to the lower end of a so-called circulating head to prevent spillage of fluid or xe2x80x9cmudxe2x80x9d when the kelly or circulating head are disconnected from the drillstem or casing, as the case may be. The use of a mudsaver valve is desirable to prevent the aforementioned loss of xe2x80x9cdrillingxe2x80x9d fluid, to prevent unsafe operating conditions for personnel and also to minimize contamination of the environment in the vicinity of the drilling operation.
Prior art mudsaver valves are characterized, generally, by a poppet type closure member which is held against a valve seat by a spring. However, in many instances, solid particulates are distributed throughout the drilling fluid, such as lost circulation material, which become trapped between the valve closure member and the valve seat resulting in the mudsaver valve not closing completely, and thus the loss of drilling fluid out of the circulating head or conduits which supply the fluid during operations.
Another problem associated with operations which include the use of prior art mudsaver valves pertains to the inability to at least reliably equalize the pressure between the casing or drillstem interior passage and the conduit to which the mudsaver valve is connected. Fluid pressure in the so-called standpipe or conduit to which the mudsaver valve is connected for supplying fluid to the drillstem or casing should be reduced to substantially the same pressure as the fluid in the drillstem or casing at the upper end thereof prior to disconnection and withdrawal of the circulating head and mudsaver valve from the casing. If fluid pressure should increase in the casing beyond a reasonable value which would permit disconnection of the circulating head from the casing this pressure can be monitored by suitable instruments connected to the fluid supply conduit or standpipe connected to the circulating head. Accordingly, the mud saver valve should be operable to substantially equalize the fluid pressure in the drillstem or casing with that in the standpipe or other fluid supply conduit before disconnecting the fluid circulating head or casing installation equipment from the drillstem or casing.
The above-mentioned problems associated with prior art mudsaver valves and operations which utilize mudsaver valves together with other improvements which have been desired in mudsaver valves have been substantially met by the present invention.
The present invention provides an improved mudsaver valve for use in well drilling and casing installation operations. The present invention also provides an improved mudsaver valve and flowback valve assembly.
In accordance with one important aspect of the present invention a mudsaver valve is provided which is characterized by an elongated tubular mandrel shaped closure member which is slidably disposed in a generally cylindrical valve body and is spring biased to a valve closed position, but responds to a pressure differential acting thereacross to move to a valve open position. The chance of improper valve closure is minimized by the configuration of the tubular valve closure member which is provided with lateral or radially extending ports and wherein the tubular closure member is disposed in engagement with a cylindrical annular seal or packoff member. The annular seal or packoff member functions as a seal or valve xe2x80x9cseatxe2x80x9d, is mounted in the mudsaver valve body, is operable to sealingly engage the closure member and is operable to minimize damage to the closure member or the packoff member when particulate laden fluid is being pumped through the mudsaver valve.
In accordance with another aspect of the present invention an improved mudsaver valve is provided in combination with a flowback valve which is operable to equalize fluid pressure between a tubular casing or drillstem member in which the mudsaver valve is disposed and a fluid supply conduit to which the mudsaver valve is connected. The flowback valve itself is of novel configuration and is also operable to prevent recirculation of fluid through the flowback valve when fluid is being purposely pumped through the mudsaver valve and into a casing, drillstem or the like. Still further, the flowback valve is configured to minimize damage to itself or loss of its sealing or shutoff function when exposed to particulate laden fluids.
Still further, the present invention provides an improved mudsaver valve and flowback valve assembly which requires a minimum number of uncomplicated, rugged and reliable parts which may be easily replaced, if required. The mudsaver and flowback valve assembly is configured to be reliable and long lived in operation by providing the valve assembly with wear members which can be easily replaced without requiring replacement of major valve components.
Those skilled in the art will further appreciate the above-mentioned advantages and superior features of the invention together with other important aspects thereof upon reading the detailed description which follows in conjunction with the drawing.